Twenty-five meteorological balloons entered Lithuania’s territory overnight Saturday, prompting authorities to close the airspace over Vilnius Airport for more than six hours. The incident raised questions about what meteorological balloons are and why they sometimes cross borders.
What are meteorological balloons?
Although meteorological balloons are sometimes used by smugglers, they are primarily an essential tool for weather observation. Around the world, these hydrogen-filled balloons are launched daily to measure atmospheric conditions at various altitudes and to support scientific research.
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In Lithuania, such balloons are released every night at midnight UTC from the Kaunas meteorological station. They lift a small instrument package known as a radiosonde, which transmits real-time data on atmospheric pressure, air and dew point temperatures, relative humidity, and wind speed and direction as it ascends through the stratosphere.
These measurements are vital for understanding upper-atmosphere conditions and improving weather forecasts. Without regular radiosonde launches and meteorological data from aircraft, forecasts would be far less accurate.
Lithuanian weather balloons carry special labels identifying them as harmless scientific instruments. Experts say that if anyone finds a radiosonde after it lands, it should be safely discarded or returned to the Lithuanian Hydrometeorological Service.
How do balloons from Belarus reach Lithuania?
Meteorological balloons can be purchased online for as little as a few dozen euros, and smugglers increasingly use them to carry small loads across borders.
Hot air balloon pilot and instructor Giedrius Leškevičius explained to LRT TV that unlike hot air balloons, meteorological balloons are not steerable and their flight paths depend entirely on wind conditions. However, smugglers need little meteorological knowledge to launch them successfully.
“It’s enough to look at a weather forecast to see how the wind changes with altitude, whether it reverses direction or remains steady,” Leškevičius said. “In this case, the wind should blow from the southwest to the northwest for the balloon to travel from Belarus into Lithuania.”
He noted that because the Belarus-Lithuania border is long, a balloon could cross it in as little as an hour if strong, steady winds are blowing.
Do smugglers know where the balloons land?
On the ground, a meteorological balloon may be 1.5 to 3 meters in diameter, but as it rises to altitudes of 20 to 40 kilometres, decreasing pressure causes it to expand until the balloon bursts.
According to Leškevičius, smugglers usually know where this happens because the cargo often contains lightweight GPS trackers. These allow them to pinpoint where the balloon and its payload fall back to Earth.
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